1. Field of Invention
The invention relates generally to a photoresist film for engraving, and more particularly, to easily repositioning the film prior to pressure being applied and before the engraving.
2. Description of Related Art
Engraving is the practice of incising a design into a hard, usually, but not limited to flat surface, by cutting grooves into it. Common surfaces to engrave include glass, wood, stone or any other hard surface that will abrade away.
Traditional engraving continues to be practiced today by goldsmiths, glass engravers, monument makers, gunsmiths and others, while modern industrial techniques such as laser engraving have many important applications as well. Laser engraving is the practice of using a laser to engrave or mark an object, and it does not use tools which contact the engraving surface and it does not wear out.
Engraving applies a photoresist to the surface to be engraved to create a mask that shields some areas during a subsequent operation which engraves, dissolves, or otherwise removes some or all of the material from the unshielded areas. The photoresist is material used in several industrial processes such as photolithography and engraving to form a patterned coating on a surface.
In engraving, a photoresist is selected which is resistant to the particular engraving compound to be used. It may be a liquid applied by brushing, spraying, pouring or other means and then allowed to set, or it may come in sheet form and be applied by laminating. The surface of the object is then sandblasted through a pattern or a design cutout portion on the photoresist.
A problem with conventional photoresist films is the difficulty repositioning the film to a surface of an object such that the design can be observed on the object, and such that the precise arrangement can be confirmed, prior to adhesion. Once a conventional film is applied to the surface, it cannot be moved to a different part of the surface.
Another problem with conventional photoresist films is achieving a thin width but without weakening the film. There is a tradeoff between the thickness of the film and the strength. A thicker film is desirably stronger than a thinner material due to its composition. And a stronger film allows for a deeper engraving into an object or surface producing sharper images and a higher resolution. However, a thicker film unfortunately does not allow as many details to be engraved into an object, compared to a thinner film. Ideally, a strong film is desired to ensure the film blocks the areas which should not be engraved, but the film is thin enough to make engraving details easier.
U.S. Pat. No. 4,764,449 to Vanlseghem provides a method of forming an engraved pattern in the surface of a complex contour on an object such as a wine goblet. Vanlseghem has a photoresist laminate comprising a resist layer, a support membrane, and an adhesive layer, which are exposed with an ultraviolet light to leave a desired pattern. However, Vanlseghem's adhesive is like that of many conventional engraves, where the film's adhesive has a high degree of tack and cohesive strength. Vanlseghem's adhesive tends to bond almost instantaneously to a surface with slight contact pressure at the interface between the adhesive and the contacted surface. Since Vanlseghem's adhesive has a high degree of tack, it cannot be easily shifted, rotated, moved, or otherwise repositioned prior to applying pressure.
U.S. Pat. Pub. No. 2011/0076430 to Shigematsu contains a pressure-sensitive adhesive sheet having a base material and a pressure-sensitive adhesive layer, where the pressure-sensitive adhesive layer contains bubbles and hollow microspheres. However, Shigematsu is unrelated and not relevant to photoresist films, and instead is for a heat pack or body warmer, which is unrelated to engraving.